Traditional flame detectors use bandpass filters, allowing detection of flames in one infrared optical band by an IR detector. Generally, these filters are built to pass 4.4 μm light corresponding to hydrocarbon based flames, or to pass 2.7 μm light corresponding to hydrogen based flames. A detector will not detect a flame outside the bandwidth that it is designed to pass. Thus, a detector built for a hydrocarbon based flame will not detect a hydrogen based flame.